1. Field of the Invention
The present invention relates to an image display system, and particularly to an image display system that displays an image in such a way as to surround an observer and thereby offers a high degree of realism.
2. Description of the Prior Art
In the field of virtual reality that is aiming at presenting an image of an actually nonexistent space with a high degree of realism, it is essential to display an image representing as wide a space as possible. To achieve this, it has been becoming increasingly common to display an image not only in front of an observer but also around the observer so that the image surrounds the observer. For example, according to one conventional proposal, a box-like observation room so large as to house an observer is constructed, and an image is displayed on the side faces, on the floor face, and even on the ceiling face thereof so that the observer is surrounded by the four-, five-, or six-faced image.
In such an image display apparatus, the wall faces of the observation room are used as screens onto which enlarged images of images formed on image display devices are projected. Here, as many image display devices as the number of screens are provided, and, to permit the images formed on the image display devices to be projected onto the screens, as many projection optical systems as the number of screens are provided. To prevent the light projected from the projection optical systems from being intercepted by the body of the observer, it is customary to use transmissive screens onto which an image is projected from outside the observation room. Moreover, to minimize the size of the entire apparatus, mirrors for turning the optical path of the projected light are arranged between the projection optical systems and the screens.
Furthermore, to give perspective to the displayed image (i.e. to make the displayed image three-dimensional), a conventional method is used in combination whereby two images that differ in their view points so much as to correspond to the parallax between the right and left eyes are displayed alternately, with one image directed to the right eye and the other directed to the left eye. In this case, the observer observes the image while wearing goggles provided with shutters that are switched between a light transmitting state and a light intercepting state in synchronism with the alternation of the two images. Moreover, it is also common to accompany the displayed image with matching sound to offer a higher degree of realism to the observer.
In this way, there have already been realized image display apparatuses that offer a very high degree of realism by surrounding an observer with an image so that as wide a space as possible is represented by the image, and by using sound as well.
However, such conventional image display apparatuses still leave room for improvement both in their construction and in the kinds of realism they can offer. For example, as to the construction, such image display apparatuses require so many image display devices and projection optical systems as the number of screens and thus require a complex construction that makes their miniaturization difficult. Moreover, the observation room is installed on a non-mobile basis, which greatly limits the location where the projected image can be observed. As to the kinds of realism, such image display apparatuses offer solely sensation as is experienced on the earth and do not exploit senses other than sight and hearing. For example, no image display apparatus has ever been proposed that offers sensation as is experienced underwater or under low gravity.
Furthermore, conventional image display apparatuses have also the disadvantage of not permitting the image displayed with a high degree of realism to be shared by two or more observers. It is possible to house two or more observers in one observation room, but the two observers cannot be in exactly identical positions at a time, and therefore, even if the displayed image is optimized for one observer, it is not so for the other, who is thus obliged to observe the image with a lower degree of realism.
It is possible to construct a plurality of observation rooms to permit the observer in every observation room to observe an optimized image. This construction, however, is equivalent to constructing a plurality of image display apparatuses independently, and thus cannot provide each observer with the sensation that the other observers are around.